Dental chair



H. H. KEITH.

(No Model.)

DENTAL CHAIR.

No. 367,300. Patented July 26, 1887 UNITED STATES PATENT IOFFICE.

HENRY H. KEITH, OF ST. LOUIS, MISSOURI.

DE NTAL. CHAIR.

SPECIFICATION forming part of Letters Patent No. 367,300, dated July 26, 1887,

Application filed April 29, 1886.

To all whom, it may concern.- 7

Be it known that I, HENRY H. KEITH, of the city of St. Louis, in the State of Missouri, have invented a certain new and useful Improvement in Dental Chairs, of which the following is a full, clear, and exact description, reference being had to the accompanying d rawings, forming part of this specification, and in which- Figure I is an outline perspective view of a dental chair(known as the f Morrison chair) having my improvement. Fig. II is an enlarged perspective view of the hand-crank.

Figs. III and IV are enlarged details showing the ratchet-wheel with the spring-dog and cam in their different positions.

In dental chairs there are appliances for raising and lowering the seat-frame audits appendages, the appliance being generally turned by a hand-crank.

My improvement consists in the peculiar construction of the crank, enabling it to be worked by the foot.

A is the frame ofa dental chair, and B the seat-frame, of which the foot-rest 0, back D, and arms E are appendages.

At F are cog-racks on the upright of the main frame, with which engage spur-wheels upon the shaft G, which hasjournal-bearings on the seat-frame B, so that by the turning-of the shaft the seat, with its appendages, may be raised or lowered. The shaft has a ratchetwheel, H, which engages with a dog or pawl, I, that acts to support the seat at any desired elevation, by preventing the rotation of the shaft G in the direction to admit of such descent, while at thesame time the shaft is permitted to turn in the other direction for the elevation of the chairseat. These parts'may have any usual construction. No novelty is claimed in them, nor is any detailed description needed, as they are well known, (for instance, in the Morrison dental chair, described in his reissued patent, dated May 15, 1887.)

Upon the angular end G of the shaft is fitted the hand-crank. This has a ratchet or notched wheel, J, whose socket j fits the end G, and which turns in the head K of the crank.

L is a pawl or dog, whose end Z is forced Serial No. 200,607. (No model.)

into the notches of the wheel J by a spring, M, so as to enable the turning of the'shaft G 'by the crank in a direction to raise the seatposition shown in Fig. IV the pawl is allowed to engage the wheel J. The cam is turned by a thumb-piece, n.

O is the shank of the crank and P is the handle; It is a'stirrup hung onto the handle to give means for working the crank by the foot of the operator.

It will be understood that the hands of the operator may be engaged when it is desired to lift the seat; and at such times it can very easily be done by applying the foot to the crank and imparting to it an oscillatory movement.

The weight of the chair, it will be understood, is always sufficie'ntto carry it down when the dog I has been raised and the handcrank allowed to turn backward.

The ratchet connection has great advantages over a simple crank in this connection, as it can at any time be placed in any position' out of the way of the operator, and need never be used in a position where the strength of the operator would. be expended at a disadvantage.

I claim as my invention 1. The combination, with the elevating-shaft of a dental chair, of a hand-crank provided with a receptacle for the foot separate from the handle, whereby a combined foot-lever and hand-crank is produced, substantially as set forth.

2. The combination, with ahand crank having a handle, of a stirrup depending from said handle, substantially as and for the purpose set forth.

HENRY H. KEITH.

Witnesses:

SAML. KNIGHT, Enw. S. KNIGHT. 

